Reference is made to commonly assigned, co-pending application Ser. No. 09/621,292 entitled FLASH CAMERA WITH TOP-POSITIONED FLASH CHARGE BUTTON and filed Jul. 20, 2000 in the names of Joel S. Lawther, Jude A. SanGregory and Michael R. Allen.
The invention relates generally to the field of photography, and in particular to an electronic flash unit for use in a camera. More specifically, the invention relates to an electronic flash unit with an integrated flash charge switch.
Electronic flash illumination, as used in photography, is produced by an instantaneous electric discharge between two opposite end electrodes in a gas-filled flash tube. In practice, the electrical energy for the discharge is stored in a capacitor. The main components of an electronic flash unit are therefore the power supply, the capacitor, the triggering circuit, and the flash tube itself usually with a partially surrounding reflector.
At present, electronic flash units are built into a broad spectrum of cameras, from disposable one-time-use cameras to sophisticated single-lens reflex cameras. Typically, they use a high-frequency oscillator to convert the dc voltage from a battery to an ac voltage that""s stepped up in a transformer. This high voltage is rectified back to dc and stored in a main capacitor connected to a glass-walled flash tube filled with xenon and small amounts of other gases. The oscillator, the rectifier, the transformer, and the battery constitute a flash charging circuit that is activated when a flash charge switch is closed, often by manually depressing a flash charge button at the front of a camera. A monitoring circuit ignites a flash ready light when the stored voltage in the main capacitor approaches a peak capacity. The stored voltage cannot discharge through the flash tube until the xenon becomes ionized. This happens when the camera""s shutter-flash synchronization switch closes, dumping the charge from a small trigger capacitor into an ignition coil connected to the flash tube, which produces a brief burst of voltage applied to the glass wall of the flash tube via a third (triggering) electrode. The xenon is then ionized to provide a conductive path for the stored voltage from the main capacitor, which results in the electronic flash illumination.
Often, the flash tube is positioned between a front transparent or translucent cover-lens and a rear reflector that partially resides in a cut-out in a flash circuit board. Respective electrical conductors contact the two opposite end electrodes of the flash tube to electrically connect them to the flash circuit board. See prior art U.S. Pat. No. 6,075,948 issued Jun. 13, 2000.
The cross-referenced application discloses a flash camera including a taking lens, a viewfinder, a flash cover-lens, a shutter release button manually depressible to initiate a film exposure, a flash charge button manually depressible to charge a flash capacitor, and a six-faced polyhedron housing having a front face with a front opening for the taking lens, a front opening for the viewfinder and a front opening for the flash cover-lens, and having a top face perpendicular to the front face and with a top opening at least partially surrounding the shutter release button. According to the invention, the top face has a top opening at least partially surrounding the flash charge button and closer to the front opening for the flash cover-lens than to the front opening for the viewfinder and the front opening for the taking lens.
An electronic flash unit comprising a flash circuit board, an illumination-producing flash tube having two opposite end electrodes, respective electrical conductors contacting the opposite end electrodes to electrically connect them to the flash circuit board, an energy-storing capacitor electrically connected to the flash circuit board and chargeable to a storage capacity sufficient to cause the flash tube to provide illumination, and a flash charge switch which when manually closed permits the capacitor to be charged, is characterized in that:
the flash charge switch has a movable closing-switch element that forms an integral single piece with one of the electrical conductors contacting the opposite end electrodes of the flash tube.